There are many examples of inorganic compounds that combine a metal with a group 15 element in the stoichiometric ratio of 2:3. Many Transition and rare earth metals, for example, form oxides with this stoichiometry. The 2:3 stoichiomety is also observed for compounds that combine group 13 and group 16 elements, such as M.sub.2 O.sub.3, M.sub.2 S.sub.3, M.sub.2 Se.sub.3 ant M.sub.2 Te.sub.3, where M is aluminum, gallium, indium or thallium.
Many of these 2:3 stoichiometric ratio compounds have significant technical applications, especially when in the form of powders, films, coatings and electronic materials. As one example, aluminum oxide (Al.sub.2 O.sub.3 or alumina), has been proposed for decoupling capacitor applications, as passivating layers and as radiation resistive films for semiconductor devices; with silicon dioxide, aluminum oxide can form insulator films for MOSFET (metal-oxide-semicorductor field effect transistor) and for MISFET (metal-insulator-semiconductor field effect transistor). Aluminum oxide powders, films and coatings are also useful in protecting materials against corrosion effects.
Several techniques are known for producing powders, films and coatings. Conventional organometallic chemical vapor deposition (OMCVD), for example, generally involves chemical reactions between two or more gas phase precursors. Frequently, these reactions occur at high temperatures, raise safety-related concerns and must be carefully controlled with respect to the stoichiometry of the reactants.
Some of these problems are addressed by film growing techniques which involve nct a reaction between two or more compounds but rather the pyrolysis of a single suitable precursor. Films of gallium nitride and gallium arsenide, for example, have been produced by single source precursor processes.
Generally, it is desirable to select single source precursors which contain elements and preexisting chemical bonds that also characterize the powder, film or coating of interest. Typically, single source precursors also contain organic groups or moieties, sometimes referred to as organic licands, that can be eliminated by heating or pyrolysis of the precursor.
With respect to the group 13/16 inorganic compounds discussed above, several single source precursors have been investigated in relation to making metal oxide films or coatings. For example, gallium oxide (Ga.sub.2 O.sub.3) films have been made from gallium tris-hexafluoroacetylacetonate, aluminum oxide (Al.sub.2 O.sub.3) films from aluminum hexafluoroacetylaicetonate, aluminum acetylacetonate, aluminum 2-ethylhexainoate, aluminum tri-sec-butoxide and aluminum tri-iscopropoxide and a mononuclear indium (III) benzoate has been investigated as a possible precursor for indium oxide (In.sub.2 O.sub.3).
All of these precursors present disadvantages. For example, their use has been limited to gaseous phase deposition techniques. Furthermore, these precursors do not have the 2:3 metal to group 16 heteroatom ratio which is typical of the targeted inorganic material but instead contain excess oxygen.